/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to you under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.calcite.rel.rules;

import com.google.common.collect.Lists;
import org.apache.calcite.plan.RelOptRule;
import org.apache.calcite.plan.RelOptRuleCall;
import org.apache.calcite.rel.RelNode;
import org.apache.calcite.rel.core.Join;
import org.apache.calcite.rel.core.Project;
import org.apache.calcite.rel.core.RelFactories;
import org.apache.calcite.rel.core.SemiJoin;
import org.apache.calcite.rel.logical.LogicalSemiJoin;
import org.apache.calcite.rel.type.RelDataTypeField;
import org.apache.calcite.rex.RexNode;
import org.apache.calcite.tools.RelBuilderFactory;
import org.apache.calcite.util.Util;

import java.util.ArrayList;
import java.util.List;

/**
 * Planner rule that pushes a {@link org.apache.calcite.rel.core.Project}
 * past a {@link org.apache.calcite.rel.core.Join}
 * by splitting the projection into a projection on top of each child of
 * the join.
 */
public class ProjectJoinTransposeRule extends RelOptRule {
  public static final ProjectJoinTransposeRule INSTANCE =
      new ProjectJoinTransposeRule(
          PushProjector.ExprCondition.TRUE,
          RelFactories.LOGICAL_BUILDER);

  //~ Instance fields --------------------------------------------------------

  /**
   * Condition for expressions that should be preserved in the projection.
   */
  private final PushProjector.ExprCondition preserveExprCondition;

  //~ Constructors -----------------------------------------------------------

  /**
   * Creates a ProjectJoinTransposeRule with an explicit condition.
   *
   * @param preserveExprCondition Condition for expressions that should be
   *                              preserved in the projection
   */
  public ProjectJoinTransposeRule(
      PushProjector.ExprCondition preserveExprCondition,
      RelBuilderFactory relFactory) {
    super(
        operand(Project.class,
            operand(Join.class, any())),
        relFactory, null);
    this.preserveExprCondition = preserveExprCondition;
  }

  //~ Methods ----------------------------------------------------------------

  // implement RelOptRule
  public void onMatch(RelOptRuleCall call) {
    Project origProj = call.rel(0);
    final Join join = call.rel(1);

    if (Util.projectHasSubQuery(origProj)) {
      return;
    }



    // locate all fields referenced in the projection and join condition;
    // determine which inputs are referenced in the projection and
    // join condition; if all fields are being referenced and there are no
    // special expressions, no point in proceeding any further
    PushProjector pushProject = null;
    if (join instanceof LogicalSemiJoin) {
      pushProject = new PushProjector(origProj, join.getCondition(), join, PushProjector.ExprCondition.FALSE, call.builder());
    } else {
      pushProject = new PushProjector(origProj, join.getCondition(), join, preserveExprCondition, call.builder());
    }

    if (pushProject.locateAllRefs()) {
      return;
    }

    // create left and right projections, projecting only those
    // fields referenced on each side
    RelNode leftProjRel =
        pushProject.createProjectRefsAndExprs(
            join.getLeft(),
            true,
            false);
    RelNode rightProjRel =
        pushProject.createProjectRefsAndExprs(
            join.getRight(),
            true,
            true);

    // convert the join condition to reference the projected columns
    RexNode newJoinFilter = null;
    int[] adjustments = pushProject.getAdjustments();
    if (join.getCondition() != null) {
      List<RelDataTypeField> projJoinFieldList = new ArrayList<>();
      projJoinFieldList.addAll(
          join.getSystemFieldList());
      projJoinFieldList.addAll(
          leftProjRel.getRowType().getFieldList());
      projJoinFieldList.addAll(
          rightProjRel.getRowType().getFieldList());
      newJoinFilter =
          pushProject.convertRefsAndExprs(
              join.getCondition(),
              projJoinFieldList,
              adjustments);
    }

    List<RexNode> operands = null;
    List<RexNode> innerOperands = null;
    if(join instanceof LogicalSemiJoin){
      List<RelDataTypeField> projJoinFieldList = new ArrayList<>();
      projJoinFieldList.addAll(join.getSystemFieldList());
      projJoinFieldList.addAll(leftProjRel.getRowType().getFieldList());
      projJoinFieldList.addAll(rightProjRel.getRowType().getFieldList());
      if (((LogicalSemiJoin) join).getOperands() != null) {
        operands = convert(projJoinFieldList, ((LogicalSemiJoin) join).getOperands(), pushProject);
      } else {
        operands = Lists.newArrayList();
      }

      // create a new join with the projected children
      Join newJoinRel = ((LogicalSemiJoin) join).copy(join.getTraitSet(),
              newJoinFilter,
              leftProjRel,
              rightProjRel,
              join.getJoinType(),
              join.isSemiJoinDone(),
              operands);

      // put the original project on top of the join, converting it to
      // reference the modified projection list
      RelNode topProject = pushProject.createNewProject(newJoinRel, adjustments);

      call.transformTo(topProject);
      return;
    }


    // create a new join with the projected children
    Join newJoinRel =
        join.copy(
            join.getTraitSet(),
            newJoinFilter,
            leftProjRel,
            rightProjRel,
            join.getJoinType(),
            join.isSemiJoinDone());

    // put the original project on top of the join, converting it to
    // reference the modified projection list
    RelNode topProject =
        pushProject.createNewProject(newJoinRel, adjustments);

    call.transformTo(topProject);
  }

  private List<RexNode> convert(List<RelDataTypeField> projectJoinFieldList, List<RexNode> operands,
                                PushProjector pushProject) {
    List<RexNode> rexNodeList = Lists.newArrayList();
    for (RexNode rexNode : operands) {
      rexNodeList.add(pushProject.convertRefsAndExprs(rexNode, projectJoinFieldList, pushProject.getAdjustments()));
    }
    return rexNodeList;
  }
}

// End ProjectJoinTransposeRule.java
